Turning on PSU turns on the Pc without pressing power

I just finished my first build, and have run into a problem.

Before I put everything into my case, I did an external build to test everything, everything worked, I even installed OS.

When I put everything into the case, which I finished a few minutes ago, I pressed the PSU button.

I didn't press the power button, yet everything turned on (fans spinning, etc.)
ANother strange thing is that the monitor wasn't picking up the signal from the video card.

Switching the psu on/off turned on/off the parts.

What could be the problem?

I even tried pulling out the front panel power plug and stuff, and the psu still turns on everything.

The psu shouldn't control the on/off, the motherboard power should...
13 answers Last reply
More about turning turns pressing power
  1. the bios has an option thats called "boot after power lose". If this is set to ON the computer will boot itself every time you unplug it or turn off the PSU.
    Change this setting to OFF.
  2. I don't think that's the problem, because in my external build, I didn't change any settings like that.

    Also, I can't even access BIOS or anything because my monitor isn't even picking up the signal from the PC!

    What else could be the problem?
  3. Try reconnecting the front panel power plug but reversing the polarity from the way you had it before.
  4. Will that do anything? I've tried powering the psu WITHOUT the power plug even inserted into the motherboard, and it still turns it on
    And I don't see anything on my monitor...
  5. Since it worked breadboard, you must have done-not done something to change that state. I suggest checking the standoffs to make sure nothing is shorted. Each should have a screw and no extra standoffs should be installed. Remove and re-install all your connectors. There may be a miss-wiring of the leads from the MB to the case switches and indicators. Remove and re-seat all the memory modules and video card. The basic procedure is to diconnect all devices but 1 stick of ram, the HD and the video card. See if it boots with signal. Then add back in everything one at a time. From what you describe I am betting on a mis-wire or something shorting the MB. GL
  6. I took everything out of the case for another breadboard test -

    but the same problem was there-

    I switched on the psu, and before I turned on the computer, the fans started spinning and it made the startup sounds, just like the problem when it WAS in the case.

    Then I noticed something with the ATX power connector from the motherboard -

    one of the pins on the power connector wasn't there. Could that be the problem?

    I don't think I could've broken that wire though...

    the pin on the motherboard is still there, but not the power connector (the wire on the psu)

    This is the missing pin on the connector (the asterisk is the missing pin):

    O O O O O O O O O O O O
    O O O O O O O * O O O O

    Or is this normal, and I just never noticed it?
  7. You have access to another PSU? for testing that?
    One more thing is, Is there any PCI cards in? if so remove them and test again; just MB and CPU and no front panel connectors
    Maybe the wires of the connectors are in constant contact together.
  8. I checked another psu, it also has no wire there so it must be normal.

    I just removed everything from the case, all pci cards including video cards (I used the integrated graphics connector)

    Only thing I left connected:
    CPU, CPU fan, and RAM.

    I powered PSU, and before I shorted the power pins, the cpu fan started spinning and the monitor stopped showing the "cable not connected" message, and instead went blank.

    What could be the problem?

    Do you think I damaged my motherboard?
  9. What should I do to get it to work?
  10. Ok, so I somehow managed to get the breadboard to work again.
    (which is a relief - I was afraid I fried my mobo)
    But I still need to figure out how to stop the problem of the PSU turning on everything before main power is on...

    To turn it on I still have to short the power pins, but before I do the fans are running.

    The first reply said something about "boot after power lose"
    How do I do this? I can't find that setting.
    I might try going on the BIOS again and see if I do anything.
  11. Speaking of BIOS; is that the latest version?
  12. BIOS->APM(Advanced Power Management) ; it must be there

    ACPI Functions something like this:

  13. turned out to be a faulty psu.

    Thanks for all the answers though...
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